1. (Field of the Invention)
The present invention generally relates to a magnetic tape cartridge and, more particular, to the magnetic tape cartridge of a type having a single tape reel for the support therearound of a length of magnetic recording and/or reproducing tape.
2. (Description of the Prior Art)
The single-reel tape cartridge, i.e., the tape cartridge of the type referred to hereinabove, is currently available in the market as an external storage module that is used in association with, for example, a computer. As disclosed in, for example, the Japanese Laid-open Patent Publications No. 62-66486 and No. 8-63940, the single-reel tape cartridge generally comprises a tape reel rotatably accommodated within a generally rectangular flattened box or casing. A length of magnetic recording tape is accommodated within the flattened box and is connected at one end to the tape reel and at the opposite end provided with a connecting piece that is utilized when the length of magnetic tape is to be drawn out of the flattened box.
More specifically, FIG. 7 illustrates the prior art single-reel tape cartridge believed to be pertinent to the present invention. As shown therein, the tape reel 53 used therein includes a cylindrical hollow boss 52 having opposite ends formed integrally with upper and lower radial flanges 50 and 51. The cylindrical hollow boss 52 is closed at one end by a perforated end wall and accommodates therein a reel retainer 54 movable between engaged and disengaged positions and cooperable with the perforated end wall to prevent the tape reel 53 from rotating idle when in the disengaged position, that is, so long as the tape cartridge is not in use. A ring-shaped iron plate 55 is secured to an outer surface of the perforated end wall of the hollow boss 52 in coaxial relation with the perforation in the end wall and is adapted to be magnetically coupled with a rotary drive element (not shown) of a tape drive externally to the tape cartridge. An annular portion of the outer surface of the perforated end wall radially outwardly of the ring-shaped iron plate 55 provides a surface engagement SE engageable with the rotary drive element to receive a rotational force from such rotary drive element. So far illustrated, the engagement 56 is in the form of a pattern of surface indentations.
The reel retainer 54 comprises a compression coil spring 57, a disc-shaped retainer plate 58 having a cylindrical hollow slide boss 59 and a passive pin 60 both formed integrally with the retainer plate 58 in coaxial relation thereto so as to extend outwardly therefrom in respective directions opposite to each other. While the compression coil spring 57 encircling the slide boss 59 applies a biasing force to the retainer plate 58 with a lower surface of retainer plate 58 held in contact with a raised seat 61 integral with the perforated end wall of the hollow boss 52, the passive pin 60 is engaged in the perforation in the perforated end wall of the hollow boss 52 and also in the perforation of the iron plate 55. Respective mating surfaces 62 of the retainer plate 58 and the raised seat 61 are indented in a sense reverse to each other so that they can be interlocked with each other unless the retainer plate 58 is displaced away from the raised seat 61.
A top panel of the flattened box has a guide post 63 formed integrally therewith so as to protrude into the hollow of the hollow boss 52 and relatively slidably projecting a distance into the hollow of the slide boss 59. Thus, the slide boss 59 normally urged by the spring 57 in one direction with the retainer plate 58 held in contact with the raised seat 61 can displace axially in the opposite direction against the spring 57, having been guided along the guide post 63 integral with the top panel of the flattened box.
Thus, unless the passive pin 60 is shifted upwardly against the spring 57 by the rotary drive element of the tape drive during the use of the tape cartridge to disengage the retainer plate 58 from the raised seat 61, the tape reel 53 cannot rotate idle about the longitudinal axis thereof. However, once the retainer plate 58 disengages from the raised seat 61 with the passive pin 60 shifted upwardly against the spring 57, the drive element of the tape drive is magnetically coupled with the iron plate 55 and, at the same time, engages the surface engagement 56 to thereby transmit the rotational force from the drive element to the tape reel 53 and, hence, to drive the tape reel 53 about the longitudinal axis thereof.
It has, however, been that the prior art single-reel tape cartridge of the structure discussed above have numerous problems. As discussed above, in order to set the tape reel 53 in a position ready to be driven, the passive pin 60 has to be pushed upwardly against the spring 57 to bring the reel retainer 54 to the disengaged position with the retainer plate 58 disengaged from the raised seat 61. Drive of the drive element can be transmitted to the tape reel 53 when and after the drive element is magnetically coupled with the iron plate 55 with the indented mating surfaces 62 engaged with each other. With this drive transmission system, it often occurs that the drive of the drive element cannot be assuredly transmitted to the tape reel 53 by the following reason.
Specifically, during the condition in which the reel retainer 54 is in the disengaged position with the retainer plate 58 disengaged from the raised seat 61 integral with the tape reel 53, the reel retainer 54 itself may tilt with a local area of the retainer plate 54 consequently held in contact with a corresponding portion of the raised seat 61, allowing either the drive element to be rotated idle relative to the tape reel 53 or the tape reel 53 itself to be rotated in a tilted fashion.
Since the drive element must bear a substantially entire quantity of the biasing force of the spring 57 transmitted thereto through the retainer plate 58 and the passive pin 60 when the reel retainer 54 is in the disengaged position, the tape reel 53 is susceptible to tilting. Also, since the drive element and the tape reel 53 are drivingly coupled with each other by means of the magnetic force of attraction developing between the drive element and the iron plate 55, there is no assurance that the entire quantity of the drive of the drive element can be transmitted to the tape reel 53 and, rather, the presence of a magnetic gap between the drive element and the iron plate 55 opens to the possibility of the tape reel 53 to tilt.